A Simple Structure of High Sensitivity of Plasmonic Photonic Crystal Fiber Sensors with Minimal Air Hole Density in Fiber Cladding

Surface plasmon resonance (SPR)-based photonic crystal fiber (PCF) sensors have advanced significantly in recent years, yet many proposed sensors suffer from low sensitivity or complex fabrication processes that use many air holes in fiber cladding that are unsuitable for real-time applications. To address this, we propose and analyze a reduced air hole of the SPR-PCF with only four circular air holes in the cladding. This design choice simplifies fabrication and reduces costs compared to a sensor with a larger number of air holes. Using the finite element method (FEM), we demonstrate that our sensor achieves a maximum sensitivity of 11,000 nm/RIU along with the figure of merit of 220 1/RIU and a maximum theoretical resolution (MTR) of 9.09 × 10−6 RIU (RIU refers to the refractive index unit) using the wavelength interrogation technique. We believe that the designed SPR-PCF sensor holds promise for detecting biomolecular and biological analyte because of its high sensitivity and simple structure. Notably, the smaller number of air holes in our design produces greater sensitivity than previously reported work that uses more air holes in the fiber cladding. To our knowledge, this represents the lowest number of circular air holes used in PCF fiber cladding for refractive index sensing, highlighting our proposed sensor design's novel and practical approach.